The invention relates to a method for determining an intersection-torque in a driving line of a motor vehicle having an automatic transmission.
Modern automatic transmissions are controlled by an electronic transmission control (EGS) which always communicates with sensors and other control equipment and computers of different units via a CAN (Controller Area Network) databus for the automatic selection of a shift program deposited in the electronic transmission control describing, e.g. an identification of a driver type as disclosed in the publication "ATZ Automobiltechnische Zeitschrift" 94 (1992), an environment related detection, a detection of a driving situation or a detection of a manual engagement and for gear selection dependent on a situation.
When detecting the driving situation, such as uphill drive or downhill, great importance is attached to an accurate evaluation of the driving line dynamics. Intersection-torques, such as motor torque, transmission output torque, or tractional resistance torque constitute important values, since fromthem the electronic transmission control can deduce additional values, such as an angle of the road ahead.
From the practice is known a method for determining a driving line intersection-torque in which a stationary torque is calculated from the product of the speed ratio and the motor torque. A medium value is thus obtained, but thus is very inaccurate.
Another known solution comprises drawing up a mathematical model equation to describe single axle drive line dynamics consisting of the inertias of the shafts and the number of revolutions thereof. Therewith are calculated the intersection-torques, such as the load torque, and derivations are made therefrom, however, the result is ridden with considerable inaccuracies. The parameters derived from a torque thus calculated are accordingly still more imprecise and often no longer utilizable.
Therefore, the known methods deliver sufficiently accurate results only for a static operation such as continuous uphill drive or a gradient over a long period of time with a very steep road angle.
However, a dynamic detection of the intersection-torques of the driving line was not possible.
Another disadvantage of said method is the very high parametering expense on each vehicle, i.e. each motor-transmission combination.
From control techniques are known control methods with a so-called state description with which can be examined systems having several input and output variables. Such state controls are used in working machines when high demands are imposed on dynamic quality control.
States variables carry the information concerning the dynamic characteristic of a controlled system or of a method. The state control makes use of this information by measuring all state variables and restoring them to the input of the control system.
For physical reasons or reasons of cost, individual state variables often cannot be measured wherefore said state variables have to be calculated from measured state variables. This is performed by state monitors which themselves constitute control systems. This presupposes that the controlled system or the transmission system can be observed, i.e. that by measuring the output variables the initial state of the state variables can be determined. Here the input variable must be known and the observation time determined.
To effect the observation, the controlled system forms a mathematical model in the manner of the state equation of the monitor. The section model is connected parallel to the controlled system, the input variable acting upon both systems. The section model is complemented by a control in which the output variables of controlled method and monitor are compared with each other. The difference retroacts on the section model via a monitor vector.
An interference level acting upon the controlled method can also have the meaning of an initial value. Interferences impair the excellence of the state control and of the state observation. But by using interference level monitors, it is also possible to determine and compensate interference levels. For the calculation of the interference level monitor, an interference level model is needed. The interference level, acting upon the controlled method, is to be compensated by means of the monitored interference signal. The remaining control difference is adjusted to zero with the modulation of the interference level.
In control techniques, it has been found that such a state control with interference level monitor has the best quality of control.
The problem on which this invention is based is to make available a method for determining an intersection-torque in a drive line of a motor vehicle having an automatic transmission with which the intersection-torques can be very precisely and dynamically calculated.
According to the invention this problem is solved by a method according to claim 1.